Cryptographic devices for use with a data terminal in a data network are very sensitive devices with respect to operational reliability. Function errors occurring in the cryptographic device directly affect data transmission in the network. This can lead to a transmission of data with corrupted information, which in some circumstances cannot be immediately detected by the network subscribers. It is therefore necessary to display a malfunction in the cryptographic device immediately.
By the very nature of their function, the design of cryptographic devices is very complex and they cannot be exchanged arbitrarily for reasons of security and cost. It is therefore necessary to detect and to identify immediately any function errors occurring, and to rectify these errors.
It is therefore the object of the invention to design a cryptographic device of the type mentioned at the beginning in such a way that function errors occurring in the cryptographic device can be reliably detected and identified.